Ringworld

Ringworld is a Hugo and Nebula award-winning 1970 science fiction novel by Larry Niven, set in his Known Space universe. The work is widely considered one of the classics of science fiction literature. It is followed by three sequels, and it ties in to numerous other books in the Known Space universe.

Ringworld engineering

The "Ringworld" is an artificial ring about one million miles wide and approximately the diameter of Earth's orbit (which makes it about 600 million miles in circumference), centered about a star, and rotating to provide an Earthlike artificial gravity, with a habitable flat inner surface equivalent in area to approximately three million Earth-sized planets. Walls 1000 miles tall along the edges keep in the atmosphere. The Ringworld could be regarded as a thin slice of a Dyson sphere, with which it shares a number of characteristics. Niven himself thinks of the Ringworld as "an intermediate step between Dyson spheres and planets."

Related Topics:
Circumference - Artificial gravity - Dyson sphere

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"Ringworld", or more formally, "Niven ring", has become a generic term for such a structure, which is an example of what science fiction fans call a "Big Dumb Object", or more formally a megastructure. Other science fiction authors have devised their own variants of Niven's Ringworld, notably Iain M. Banks' Culture Orbitals, best described as miniature Ringworlds, and the ring-shaped Halo structure of the video game series of the same name.

Related Topics:
Big Dumb Object - Megastructure - Iain M. Banks - Culture Orbital - Video game series of the same name

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The construction of a ringworld remains firmly in the area of speculation. If such a structure was built it could indeed provide a huge habitable inner surface, but the energy required to construct it and set it rotating is so massive (several centuries' worth of the total energy output from the Sun) that without as-yet unimagined energy sources becoming available, it is hard to see how this construction could ever be possible in a time frame acceptable to humans.

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Furthermore, the tensile strength of the material required would be on the same order as the strong nuclear force (since the artificial gravity is the same as normal gravity, the structure is comparable with a bridge with an extremely long span); nothing even remotely strong enough is known to exist in nature. In Niven's Ringworld novels, the material?which he calls scrith?is said to have been artificially produced through the transmutation of matter into the required substance. This merely gives a name to the sufficiently advanced technology that would have to be used.

Related Topics:
Strong nuclear force - Scrith - Transmutation - Sufficiently advanced technology

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Additionally, a ringworld design requires active stabilization, because it is not in inertial orbit. Though the ring itself is rotating at 1200 km/s (to approximate Earth gravity), the center of mass does not move at all. Large thrusters must be incorporated into the design to keep it centered about its star. This point gave Niven some difficulty after he published his first Ringworld novel; he was deluged with letters pointing out that "the Ringworld isn't stable" and dedicated the first sequel to a resolution of this problem. In the fourth book in the series, Ringworld's Children he creates backplot explanations for several of the imperfections in his original design of the Ringworld?and wholly glosses over others, such as that Louis Wu is worried about his dietary intake of salt since the Ringworld possesses no saline oceans, while in Ringworld's Children, the Great Ocean is described as being saline.

Related Topics:
Inertia - Orbit - Salt - Saline - Ocean

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To provide an approximation of the day–night cycle common to planets, Niven's Ringworld was also provided with a separate ring of "shadow squares" linked together (by "shadow square wires") in a ring close to the star, rotating at slightly faster than the Ringworld's spin, providing a lot of twilight, as well as a day-night cycle. These absorb a huge amount of sunlight energy, which is beamed to the Ringworld as its primary source of power. They are also not in inertial orbit, and must be actively stabilized as well. The shadow squares provide another of the imperfections "clarified" in Ringworld's Children, as five shadow squares of greater length, orbiting retrograde would provide a better day-night cycle, with less twilight.

Related Topics:
Twilight - Retrograde

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